All shafts shall be securely cribbed to a point at least 8 inches above the immediate surrounding surface and cribbing shall be maintained in good condition during the life of the mining lease: Provided, however, That at any time shafts may be permanently sealed by a reinforced concrete slab after first obtaining the written approval of the duly authorized representative of the Department of the Interior. The slab shall be so placed as to prevent caving of the ground around the shaft collar.

All shafts, prior to the expiration, surrender, or upon cancellation of the mining lease or abandonment of the property, shall be permanently sealed so as to prevent the caving of the ground around the shaft collar: Provided, however, That this requirement may be waived after first obtaining the written consent of the duly authorized representative of the Department of the Interior.

All shaft entrances not permanently sealed shall be so fenced, boxed, or covered as to prevent persons or animals from falling into the mine when the shaft is not in actual use, and such fencing, boxing, or covering shall be maintained in good condition during the life of the mining lease.

All shafts where hoisting is done shall be boxed or fenced on three sides and the fourth side equipped with a gate which shall be kept closed when access to the shaft is not necessary.

All churn drill holes shall be securely plugged to the surface unless used for ventilation or other mining purposes, in which case they shall be cased or otherwise prevented from caving or becoming a hazard to persons or animals. If cased, the casing shall extend 4 feet above the collar of the hole.